intel/compiler: Add common function for CS dispatch info

We have this small calculations repeated in each Intel driver, so move
them to a single place to be reused.  Also includes "right_mask" since
is always used in the same context and depends on the dispatch info
values.

Reviewed-by: Marcin Ślusarz <marcin.slusarz@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10504>

src/intel/compiler/brw_compiler.h

@@ -1777,6 +1777,29 @@ brw_cs_right_mask(unsigned group_size, unsigned simd_size)
       return ~0u >> (32 - simd_size);
 }
 
+struct brw_cs_dispatch_info {
+   uint32_t group_size;
+   uint32_t simd_size;
+   uint32_t threads;
+
+   /* RightExecutionMask field used in GPGPU_WALKER. */
+   uint32_t right_mask;
+};
+
+/**
+ * Get the dispatch information for a shader to be used with GPGPU_WALKER and
+ * similar instructions.
+ *
+ * If override_local_size is not NULL, it must to point to a 3-element that
+ * will override the value from prog_data->local_size.  This is used by
+ * ARB_compute_variable_group_size, where the size is set only at dispatch
+ * time (so prog_data is outdated).
+ */
+struct brw_cs_dispatch_info
+brw_cs_get_dispatch_info(const struct intel_device_info *devinfo,
+                         const struct brw_cs_prog_data *prog_data,
+                         const unsigned *override_local_size);
+
 /**
  * Return true if the given shader stage is dispatched contiguously by the
  * relevant fixed function starting from channel 0 of the SIMD thread, which

src/intel/compiler/brw_fs.cpp

@@ -9845,6 +9845,31 @@ brw_cs_simd_size_for_group_size(const struct intel_device_info *devinfo,
    return 32;
 }
 
+struct brw_cs_dispatch_info
+brw_cs_get_dispatch_info(const struct intel_device_info *devinfo,
+                         const struct brw_cs_prog_data *prog_data,
+                         const unsigned *override_local_size)
+{
+   struct brw_cs_dispatch_info info = {};
+
+   const unsigned *sizes =
+      override_local_size ? override_local_size :
+                            prog_data->local_size;
+
+   info.group_size = sizes[0] * sizes[1] * sizes[2];
+   info.simd_size =
+      brw_cs_simd_size_for_group_size(devinfo, prog_data, info.group_size);
+   info.threads = DIV_ROUND_UP(info.group_size, info.simd_size);
+
+   const uint32_t remainder = info.group_size & (info.simd_size - 1);
+   if (remainder > 0)
+      info.right_mask = ~0u >> (32 - remainder);
+   else
+      info.right_mask = ~0u >> (32 - info.simd_size);
+
+   return info;
+}
+
 const unsigned *
 brw_compile_bs(const struct brw_compiler *compiler, void *log_data,
                void *mem_ctx,